The present invention relates to a high surface area incineration product. The high surface area makes the product suitable as, for example, a coefficient of friction (COF) control filler for newsprint. When used as such a filler, the product provides improved newsprint runnability on, for example, a press. The product is prepared by a process that enables the recovery of a high surface area product comprising calcium carbonate from solid-containing material, such as effluent or waste from a plant for treating waste paper.
The processing and disposal of solid containing material from a plant for treating waste paper, such as de-inking sludges, has been a persistent problem for the paper industry, as the cost of sludge disposal continues to increase. De-inking sludges are the product of several physical separation steps designed to achieve the maximum ink removal from waste paper to produce a pulp that is as bright and speck-free as possible. A typical de-inking operation converts only 85% of its wastepaper into pulp, and the remaining 15% forms the de-inking sludge. Most de-inking processes will reject at least half of the mineral content of the wastepaper, which constitutes 50% or more of the sludge.
One of the goals of processing de-inking sludge has been to recycle useful minerals contained therein, such as calcium. However, attempts to separate minerals from the sludge typically fail for several reasons. For example, during processing of the sludge the minerals will have already been rejected by a process that uses several physical characteristics to distinguish the components of the sludge from the accepted fibers. In the case of washing, the characteristic is size, and in the case of floatation, it is a combination of size and surface chemistry. Another reason why simple separations fail is the completeness of the separation required for an acceptable product. Sludges contain up to 1% carbon black from inks, and even a 90% removal of this contaminant will produce a pigment with a brightness of less than 60% ISO, which is not acceptable for use in paper.
Methods for treating solid-containing material contained in paper treatment waste are known and are disclosed in, for example, U.S. Pat. Nos. 5,683,590; 5,846,378; and 6,063,237, the disclosures of which are all incorporated by reference herein. The processes disclosed in these patents are generally not suitable for preparing the high surface area products according to the present invention for a number of reasons. By way of example, U.S. Pat. No. 5,846,378 teaches the use of low incineration temperatures, e.g., temperatures below 750xc2x0 C. Such incineration temperatures are generally not suitable for preparing the high surface area products according to the invention.
The present inventors have discovered that a high surface area product can be obtained from solid-containing material, such as effluent from a waste paper treatment process, using a process that includes the steps of incineration, comminution, and carbonation.
The high surface area product of the present invention is useful in newsprint manufacture. High surface area affects the coefficient of friction in newsprint by adsorbing pitch material, which comprises fatty acids and triglycerides, from newsprint pulp furnish. This pitch material tends to bloom to the surface of newsprint and, acting as lubricant, causes a reduction in the coefficient of friction. This then causes slippage within a paper roll that will cause runnability problems on a newsprint press.
It is known to use calcined clay, silicas, talc, and chemical technology to increase COF in newsprint. However, certain disadvantages are attendant with these options. For example, talc and chemical technologies don""t provide ink strike-through control and light scatter to newsprint. There exists a need to provide a high surface area product that provides a high coefficient of friction, ink strike-through control, and light scatter, all in one product.
According to one aspect of the invention, there is provided a high surface area product prepared from solid-containing material by a process comprising subjecting the solid-containing material to controlled incineration at a temperature ranging from 800 to 900xc2x0 C., comminution, and carbonation, wherein the high surface area product comprises calcium carbonate.
According to another aspect of the invention, there is provided a high surface area product comprising calcium carbonate, wherein the high surface area product meets the following specifications:
According to yet another aspect of the invention, there is provided a method for preparing a high surface area product, said method comprising subjecting a solid-containing material to controlled incineration at a temperature ranging from 800 to 900xc2x0 C., comminution, and carbonation.
According to still another aspect of the invention, there is provided a method for improving newsprint runnability, said method comprising incorporating into the newsprint a high surface area product prepared from solid-containing material by a process comprising subjecting the solid-containing material to controlled incineration at a temperature ranging from 800 to 900xc2x0 C., comminution, and carbonation, and wherein the high surface area product comprises calcium carbonate.
According to still another aspect of the invention, there is provided a method for improving the coefficient of friction in newsprint, said method comprising incorporating into the newsprint a high surface area product obtained from solid-containing material by a process comprising subjecting the solid-containing material to controlled incineration at a temperature ranging from 800 to 900xc2x0 C., comminution, and carbonation.